article: When people talk about air pollution, they usually think of smog, acid rain ,and other forms  of outdoor air pollution. But did you know that air pollution also is inside homes, offices, hotels and other buildings?Indoor air pollution is more serious. The air in your home can be 2 to 100 times  more polluted than the air outdoors!In fact, some American doctors say that 50% of illnesses have something to do with polluted indoor air. Indoor air pollution is bad for our health in many ways. Young children and the old often suffer  more from air pollution. People with health problems may also suffer more when the air is polluted. Indoor air pollution can be bad for people's eyes, nose and throat. Air pollution, both indoor and outdoor, can also lead to cancer, heart disease, and even bad for the brain!In the great London fog in 1952, 4,000 people died in a few days because of air pollution!It is said that half a million young kids and women die each year in India because of indoor air pollution!
  There're many ways to reduce  indoor air pollution. Here are some of them and see if they can help you:
  Increase outdoor air coming indoors and open your windows for 15 to 30 minutes each day.
  Turn off all the lights and fans when you don't need them.
  Share your room with others when the air conditioner is running.
  Don't smoke and try to stop your family members from smoking. People who smoke are going to have trouble breathing and even die someday. If you're smart, don't ever start.
  Environment-friendly products, such as water-based paints pollute less and work well.
question: The best title of the passage is  _  .
options: The forms of outdoor air pollution The ways of reduce indoor air pollution The indoor air pollution The environment-friendly products